Soil
Soil is a natural body consisting of layers (soil horizons) that are primarily composed of minerals which differ from their parent materials in their texture, structure, consistency, colour, chemical, biological and other characteristics. It is the unconsolidated or loose covering of fine rock particles that covers the surface of the earth. Soil is the end product of the influence of the climate (temperature, precipitation), relief (slope), organisms (flora and fauna), parent materials (original minerals), and time. In engineering, soil is referred to as regolith, or loose rock material: this is the 'drift deposit' lying on top of the 'solid geology'. However, in horticulture, the term 'soil' is defined as the humic layer of topsoil, or the depth of regolith containing organic material that influences and has been influenced by plant roots and may range in depth from centimetres to many metres. Expressions such as lunar soil or Martian soil are commonly used for extraterrestrial regolith, even though there is no known biological component.
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Famous quotes containing the word soil:
“The civilized nations—Greece, Rome, England—have been sustained by the primitive forests which anciently rotted where they stand. They survive as long as the soil is not exhausted. Alas for human culture! little is to be expected of a nation, when the vegetable mould is exhausted, and it is compelled to make manure of the bones of its fathers. There the poet sustains himself merely by his own superfluous fat, and the philosopher comes down on his marrow-bones.”
—Henry David Thoreau (1817–1862)
“Let the soil squeal I am the biting man
And the velvet dead inch out.”
—Dylan Thomas (1914–1953)
“But the nomads were the terror of all those whom the soil or the advantages of the market had induced to build towns. Agriculture therefore was a religious injunction, because of the perils of the state from nomadism.”
—Ralph Waldo Emerson (1803–1882)